Recently, on account of stringent housing site circumstances, high-storied residences or apartments are being built at an ever-increasing rate. In parallel therewith, office buildings tend to shift to high-storied or super high-storied structures.
An outer or inner, separate decorative wall is usually applied as a coating on the concrete base wall of the building for finishing, no matter whether the main building structure is of steel-reinforced concrete or the steel framed reinforced concrete.
After lapse of a certain time interval after completion of construction, these decorative walls start to peel off from the concrete base all structure due to the lowered bonding strength between the building base wall and the decorative coating wall.
It is believed that such exfoliation is caused at least in part by the fact that moisture contained in the external environment permeates through small crevices or pores in the decorative wall to its back side gradually eroding away the concrete base wall.
Moisture may be permeated to the reverse surface of the decorative wall in the form of water droplets, mist or steam. Therefore, in general, the outdoor side of the wall is more susceptible to exfoliation than the indoor side, because the outdoor side is exposed directly to climatic effects.
Taking an example of a decorative mortar outer wall, this partial exfoliation grows gradually and gives rise to a phenomenon known as separation or blister.
As this blister proceeds futher to the point that the bonding strength of the mortar to the building base is unable to sustain the weight of the wall, mortar is apt to peel off and thus is in need of repair. In addition, the wall may fall down and destroy surrounding articles or injure near-by persons.
Heretofore, in order to prevent such danger, the decorative wall is repaired at proper time periods determined through periodic tests in which the wall is struck lightly as with hammers and the sound produced by the wall is scrutinized acoustically.
In the conventional practice, such repair work is done through chipping away loose mortar followed by mortar reapplication or by pouring epoxy resin or the like resin adhesives through bored holes with the aid of a pouring gun, thereby preventing the wall from peeling off or continuing the progress of separation.
However, with the former method of chipping, the amount of mortar required in recoating and the number of steps are substantially the same as those required in local reapplication of the decorative wall. Moreover, since the moisture introduced into the gaps of the blisters as water vapor in condensed into dew, the bonding strength of the poured resin adhesives may be lowered. In addition, the resin composition itself is expensive and spread to diffuse when poured into the gaps of the blisters. Therefore, a strong demand has been placed for a more effective and inexpensive repair composition.